Why am I repeating myself? You're talking to a seasoned vet here.... plan for 9 hours to SD (especially if you are IN SF/Oakland), and if you make it on less time then you'll be happy. Night driving is a good idea, but hard on the kids.
If you do go to Disneyland, avoid the 405 at all costs!!
Disneyland at Christmastime is pretty bad ass:
Great, now I want to go......
Why is Disneyland so damn fun? It really is the happiest place on earth.